1. Field of the Invention
The present invention relates to a power transmission chain and a power transmission device.
2. Description of Related Arts
For a power transmission device, such as a pulley type CVT (Continuously Variable Transmission) in an automobile, for example, an endless power transmission chain is used. As a power transmission chain, there is a type formed by coupling links aligned adjacently in the chain travel direction one to another with the use of pins and inter-pieces allowed to undergo a rolling movement with respect to each other (see, for example, References 1, 2, and 3 specified below).    Reference 1: Japanese Unexamined Patent Publication No. 2006-2784    Reference 2: U.S. Pat. No. 5,728,021    Reference 3: Japanese Unexamined Patent Publication No. 2006-226405
In the power transmission chain described above, when adjacent links bend with respect to each other, the side surface of the corresponding pin and the side surface of the corresponding inter-piece come into rolling contact with each other, which causes the contact position of these two members to move. The sectional shape of the side surface of the pin forms an involute curve. This configuration reduces a chordal action of the chain occurring when the chain is meshed with the pulleys.
The starting point of the involute curve described above is the contact portion between the pin and the inter-piece in a linear region of the chain, which is a region over which the chain extends linearly. The involute curve has a small radius of curvature in the vicinity of the starting point. Consequently, of the entire side surface of the pin, the radius of curvature is small in a portion that forms the contact portion in the linear region of the chain, and so is the contact area with the inter-piece.
As a consequence, an allowable transmission load between the pin and the inter-piece becomes smaller, which limits an allowable transmission torque of the chain. In addition, because the pin readily rolls with respect to the inter-piece in the linear region of the chain, under some vehicle running conditions, there may be a case where the linear region of the chain accidentally moves and the behavior of the chain is disturbed.
An object of the invention is to provide a power transmission chain capable of reducing the chordal action and increasing an allowable transmission torque as well as stabilizing the behavior in the linear region, and a power transmission device including the same.